In the art numerous types of sealing gaskets produced in the form of rings and designed to perform static frontal sealing, for example of pipe connections, are known. It is also known that for the industrial production of these types of gaskets it is necessary to wind up in a spiral two strips which are superimposed on each other and have physical and mechanical characteristics which are very different from each other, in particular a first strip with a high mechanical strength, for example made of steel, which forms the backing for the second strip made of a material having high insulating and sealing characteristics, but a smaller mechanical strength.
Also known are machines which perform the construction of said gaskets either semi-manually, this requiring constant monitoring and auxiliary action on the part of an operator fully overseeing the machine, or semi-automatically, as illustrated in EP 0,707,906, this document describing an automatic machine for the production of gaskets obtained by spirally winding strips with different physical and mechanical characteristics onto a support ring, which machine comprises means for feeding said support rings to a spindle, means for feeding the strips to be wound to the support ring, a unit for applying radial pressure on said rings and a unit for welding one of said strips for starting winding and for closing the gasket once winding has been completed.
The known machine has in particular a tool-holder spindle which cannot be displaced along the plane perpendicular to the tool so as to adapt to the increase in diameter of the gasket during winding of the strip; on the contrary, the entire feeding unit must be manually displaced in order to adapt it to the different dimensions of the gaskets. Similar machines according to the preamble of claim 1 are described in CN 203 955 791 and KR 101 273 079.
Although performing their function, these known machines have, however, a number of drawbacks arising from the fact that they are unable to produce automatically, and without long machine downtime needed for retooling thereof, gaskets with diametral dimensions varying between a few tens of mm and four meters.